FMRP is expressed in the majority of interneurons in the BL. (A) Schematic of a coronal view of a brain at the level of the amygdala with the BL highlighted in red. (B) Image of FMRP immunostaining at P21 showing the intense and high levels of FMRP expression in the L and BL in contrast to the much lesser immunostaining in other regions of the amygdala such as the central nucleus. (C–E) The majority of Glutamic acid decarboxylase (GAD) 65/67-positive neurons also show FMRP expression in the BL at P21. Ce, central nucleus of the amygdala; ec, external capsule; EnD, endopiriform nucleus; L, lateral nucleus of the amygdala; Pir, piriform cortex. Scale bars (B) 10 µm; (C–E) 10 µm.

Synaptic GABA release is reduced in Fmr1 KOs. (A–C) mIPSC amplitude is reduced to a greater extent by TPMPA in Fmr1 KO than in WT mice. Averaged mIPSCs from individual cells from WT (A) and Fmr1 KO (B) under control conditions and with TPMPA (200 µM) (red traces) illustrate the reduction in amplitude. (C) Averaged group data indicating that TPMPA had a significantly greater effect on mIPSCs in Fmr1 KOs at doses of 200 µM and 100 µm. This trend was also observed using a 50 µM dose, but was not statistically significant. TPMPA did not exert a significant effect on mIPSC decay. *p < 0.05. Scale bars: 2 pA, 20 ms.

Reduced number of inhibitory synapses but no changes in VGAT expression in Fmr1 KOs. (A–D) Quantitative analyses of electron micrographs of the BL show a remarkable decrease in inhibitory synapses in Fmr1 KOs with respect to WT. Excitatory synapses are decreased as well in Fmr1 KOs, although to a lesser extent (D). Arrowheads in (A) identify synaptic contacts. Detail of a symmetric (B) and asymmetric (C) synaptic contacts in the BL. Qualitative images of VGAT-immunostaining in the BL show no difference between WT (E) and Fmr1 KOs (F). Quantification of VGAT punctae (5 sections from 4 different mice) show no differences between WT and the Fmr1 KOs (G). Western blot analyses demonstrate that VGAT expression levels are similar in Fmr1 KOs and WT mice in the BL (H,I; WT: n=4; Fmr1 KO: n=4). *p < 0.05; ***p < 0.005. Scale bars: 20 µm.